WA dad who stabbed son guilty of murder

Matthew Kyle Fisher-Turner wore a tattoo reading "family first" and was saving up to buy his mother a tombstone when his pensioner father stabbed him to death in a surprise attack before watching the AFL grand final.

The 23-year-old's body was uncovered in the backyard of his family's Perth home in late October 2016 after his father Ernest Albert Fisher, 67, confessed to detectives and told them it had been buried there four weeks earlier.

Fisher initially claimed his son was "over east" but came clean after one-and-a-half hours of questioning, labelling his son a drug-using, violent, threatening and abusive "complete and utter arsehole".

He'd left two of his other children, Joshua Douglas Fisher-Turner and Hannah Jayde Fisher-Turner, to bury the body and destroy evidence while he went to a friend's house to watch the match.

The Supreme Court of WA heard the death of their mother from cancer in 2014 had triggered the unravelling of the family and the final straw was when Matthew insisted on borrowing his father's car, which Fisher needed for his footy plans.

He argued self-defence, claiming he'd been repeatedly assaulted by his son, but a Supreme Court of WA jury convicted him of murder on Thursday.

"He had no one to speak for him and so the general public didn't actually know if that was the truth or not," Patricia Kearney, the mother of a former girlfriend, Siobhan, told reporters.

"The jury obviously saw through that.

"He wasn't perfect by all means with what he had to deal with, with his very difficult family.

"It's ironic, he had a tattoo on his arm of his motto 'family first'."

She said he'd been saving up for a headstone for his mother and had been fittingly buried, for a second time, with her.

Ms Kearney was a witness at the trial, testifying Fisher had told her when she visited him in prison that he'd planned the murder, secreting two sharp knives in the shed, which he used to puncture Matthew's lung and aorta.

"The biggest nightmare of anybody would be to be killed by your own loving family, the people you think are going to be there for you," she told reporters.

Sam Woonings, who raised the alarm with police about his missing friend, said he believed Matthew would never had been found if he and Siobhan hadn't gone to the house looking for him.

"We just put that pressure down and we found him, made sure of it," Mr Woonings said outside court.